184 DR. W. X. F. WOOELANB ON THE 



respecting the physiology of these organs. Though the litera- 

 ture * concerned with the morphology and physiology of the gas 

 bladder is, of course, very considerable, yet up to the present only 

 one author (6i, 65) has attempted a complete review of the 

 subject of the present paper in the light of recent work. Further, 

 although there exist several memoirs dealing with special types of 

 " red body," yet most of these are so occupied with cytological 

 and other details that, in the opinion of the present wiiter, they 

 have failed to supply such an account and such illustrations of 

 the gross structure of these " red bodies " as to render evident 

 some of their most remarkable features. Finally, the Jaeger- 

 Nusbaum controversy calls for an independent description of these 

 unique organs, so interesting from the physiological standpoint. 



I have divided the present paper into two parts, the first of 

 which deals with the structure and the second with the physio- 

 logy of the " red bodies." With reference to the drawings 

 illustrating Part I., I have, with a few exceptions, adopted a 

 definite scheme of coloration in order to facilitate comprehension. 

 Green has been adopted to denote the internal lining epitiielium 

 of the bladder, and therefore the glandular, i. e. gas gland, epi- 

 thelium is always of this colour in the drawings, since this is but 

 a special development of the usually squamous lining epithelium ; 

 red denotes blood ; black or grey has been employed for connec- 

 tive and muscular tissue and secretion mateiial ; and yellow has 

 been used to indicate the pancreas, which is often closely 

 associa^ted in a mechanical sense with some parts of the " red 

 body." The sources and methods of preparation of my material 

 are stated in Appendix A (p. 236). 



Part I. — The Structure of the "Red Bodies" in 



VARIOUS TeLEOSTEI. 



It is necessary to recognize at the outset that the term " red 

 body " unfortunately has been applied to difi'erent structures by 

 no means equivalent to each other : thus, e. g., the " red bodies " of 

 the Common Eel are simply the two retia mirahilia, whereas the 

 "red body" of the Cod consists both of numerous small retia 

 mirabilia and of the large mass of epithelial cells called the gas 

 gland, the retia and the gas gland being, in this case, intimately 

 a,ssociated. A gas gland exists in the Eel as in all other fish 

 with " red bodies," but it is not in close connection with the 

 rete mirabile as in the Cod. This being the case, it must be 

 understood that by the term " red body " all that is meant is a 

 red mass situated in the bladder-wall, the constitution of which 

 is variable. I may add that in the vast majority of cases " led 

 body " includes both i-ete mirabile and gas gland. As an intro- 

 duction to the study of gas gland structure I shall first describe 

 the anatomy of one of the most simple as well as most common 



* For the lilevatuveand historical reviews of the entire svrhject of gas hladders up 

 to 1806 see Miliie-Edwarcls (49) and Gonriet (34) ; for more recent literature sec 

 the lists supplied by Bridge (22), Hiifner (38), Jaeger (44), Deineka (29), Keis & 

 Is'usbauui (62, 63), and at the end of the present pai)er. 



